eeropic · September 28, 2022 10:28 · Sep 28, 2022
diff --git a/y_for_x_unitbezier_paperjs.js b/y_for_x_unitbezier_paperjs.js
@@ -0,0 +1,98 @@
+// http://svn.webkit.org/repository/webkit/trunk/Source/WebCore/platform/graphics/UnitBezier.h
+class UnitBezier {
+    constructor(p1x,p1y,p2x,p2y){
+        // Calculate the polynomial coefficients, implicit first and last control points are (0,0) and (1,1).
+        this.cx = 3.0 * p1x;
+        this.bx = 3.0 * (p2x - p1x) - this.cx;
+        this.ax = 1.0 - this.cx - this.bx;
+        this.cy = 3.0 * p1y;
+        this.by = 3.0 * (p2y - p1y) - this.cy;
+        this.ay = 1.0 - this.cy - this.by;
+        Object.assign(this, {p1x, p1y, p2x, p2y})
+    }
+    sampleCurveX(t){
+        // `ax t^3 + bx t^2 + cx t' expanded using Horner's rule.
+        return ((this.ax * t + this.bx) * t + this.cx) * t;
+    }
+    sampleCurveY(t){
+        return ((this.ay * t + this.by) * t + this.cy) * t;
+    }
+    sampleCurveDerivativeX(t){
+        return (3.0 * this.ax * t + 2.0 * this.bx) * t + this.cx;
+    }
+    solveCurveX(x, epsilon){
+        if (epsilon === undefined) epsilon = 1e-6;
+        if (x < 0.0) return 0.0;
+        if (x > 1.0) return 1.0;
+        var t = x;
+        // First try a few iterations of Newton's method - normally very fast.
+        for (var i = 0; i < 8; i++) {
+            var x2 = this.sampleCurveX(t) - x;
+            if (Math.abs(x2) < epsilon) return t;
+            var d2 = this.sampleCurveDerivativeX(t);
+            if (Math.abs(d2) < 1e-6) break;
+            t = t - x2 / d2;
+        }
+        // Fall back to the bisection method for reliability.
+        var t0 = 0.0;
+        var t1 = 1.0;
+        t = x;
+        for (i = 0; i < 20; i++) {
+            x2 = this.sampleCurveX(t);
+            if (Math.abs(x2 - x) < epsilon) break;
+            if (x > x2) {
+                t0 = t;
+            } else {
+                t1 = t;
+            }
+            t = (t1 - t0) * 0.5 + t0;
+        }
+        return t;
+    }
+    solve(x, epsilon) {
+        return this.sampleCurveY(this.solveCurveX(x, epsilon));
+    }
+}
+
+
+let testPath = new Path({
+    segments: [
+        new Segment({
+            point: [180,200],
+            handleOut: [200,20]
+        }),
+        new Segment({
+            point: [400,500],
+            handleIn: [-200,60]
+        })
+    ],
+    strokeColor: "red"
+})
+
+function curveToUnit(curve){
+    const [x0, y0, x1, y1, x2, y2, x3, y3] = curve.values
+    let w = x3 - x0
+    let h = y3 - y0
+    let p1x = (x1 - x0) / w
+    let p1y = (y1 - y0) / h
+    let p2x = (x2 - x0) / w
+    let p2y = (y2 - y0) / h
+
+    let kek2 = new UnitBezier(p1x, p1y, p2x, p2y)
+
+    let steps = 40;
+    for(let i = 0; i <= steps; i++){
+        let xPos = i / steps
+        let yPos = kek2.solve(xPos)
+
+        let circ = new Shape.Circle({
+            fillColor:"blue",
+            radius: 2,
+            position: [x0 + xPos * w, y0 + yPos * h]
+        })
+    }
+}
+
+curveToUnit(testPath.curves[0])
+
+
No results found